1. Field of the Invention
The present invention relates to a heat exchanger for use as a condenser or evaporator for instance in car air conditioners, or for use as a radiator or the like.
2. Description of Prior Art
The heat exchangers of the so-called header type are now widely used as the condensers or the like for instance in the car coolers. Each heat exchanger of this type comprises a plurality of flat tubes and corrugated fins which are stacked one on another, and both ends of each tube are connected to a pair of hollow headers in fluid communication therewith.
The headers incorporated in such a heat exchanger are manufactured from a brazing sheet, or alternatively, one-piece-extruded pipes. In the former case, the brazing sheet is composed of a core having either or both sides clad with a brazing agent layer, and one sheet of a given dimension is bent to form a cylinder whose lateral edges abut against and tightly adjoined to one another.
A row of tube-insertion apertures are formed through the periphery of each header at regular intervals longitudinally of the header. The ends of the flat tubes are inserted in those apertures to a regulated depth, and are brazed thereto to be integral therewith. The tube ends must not be inserted too deep or too shallow relative to the diameter of the header.
It is however not necessarily easy to arrange the tube ends all at the regulated depth in the header in order to exactly assemble the heat exchanger. A proposal which was made to resolve this problem is disclosed in the Japanese Utility Model Laying-Open Gazette Sho. 63-80492. This prior art method of regulating the inserted depth of tubes employs a header which has an internal stopping ridge protruding from the tube's inner surface. The stopping ridge has a height midway in diametrical direction and extends a full length longitudinally of the header, so that all the tube ends bear against this ridge and align with one another at regulated insertion depth. This hollow header of such a peculiar cross-sectional shape can be extruded smoothly, but is not free from a certain problem. It is noted in this connection that the integrally adjoining of the inserted tubes and a bracket or the like to the header is generally carried out most efficiently by the one-shot brazing method. Therefore, it is preferable to employ as the header a pipe whose inner and/or outer peripheral surfaces are coated with a brazing agent layer. Such a pipe coated with that layer is however considerably difficult to extrude, from a technological point of view. Further, it is not easy to extrude a pipe composed of a relatively thin wall, thus failing to reduce the weight of the pipes as one part of a lighter heat exchanger. The work for exactly and rapidly boring the tube-insertion apertures in the pipe wall is also troublesome, due to a likelihood that the pipes tend to collapse when bored, thus impairing manufacture efficiency. Further, the internal stopping ridge present within the header will hinder an inlet and/or outlet pipes from being connected at desired portions of the header.
The heat exchangers of the described type are usually mounted on a larger rigid object such as an automobile car, by means of brackets attached to the headers. The brackets have been welded, brazed or otherwise secured to the headers. In the case of brazing, those brackets are temporarily set in place by suitable jigs before being subjected to the one-shot brazing process together with other parts of the heat exchanger. Thus, an intricate operation has been necessary for rigidly attaching the brackets to the headers.